Optimization Of Crystallization Reactor Impellers

The mixing generated by impellers in crystallization reactor plays an important role in crystallization operation process, it affects the mass transfer and heat transfer. In fact, there are already lots of research of impeller selecting on cooling crystallization and evaporation crystallization process. In order to avoid secondary nucleation, small crystal particles and crystal size distribution uneven, the impeller speed is usually very slow. But in the process of reactive crystallization, the reactants are request to be mixed as soon as possible when they are added into the reactor, to promote the reaction and uniform distribution to avoid to produce a large number of tiny crystal. The impellers speed are commonly required at higher speed operation. The existence of this contradiction makes it difficult to select the proper impeller in crystallization reactor.In this research, the impact of different impellers on reactive crystallization are studied. In the vertical stirred tank with the diameter of 0.285m, the impellers’influence on the process of potassium chloride crystallization were studied. Impellers such as CBY, PBT and RT were used in the experiment. At the same time, mixing time is also recorded to represent reaction crystallization.The experimental results shows that axial flow impellers are suitable for crystallization; large diameter of impellers are suitable for crystallization; the speed of impellers should be slow, and combined impellers are good for reaction crystallization, they are worth investigated further.